Sculpt Your Body in Six Easy Moves

Why it works: The lats are big back muscles. They're attached to your glutes (aka butt muscles) by deep tissue—right lat to left cheek and vice versa, in a crisscross. "They're connected, so making your lats stronger will help your glutes engage more effectively," says Abbie Appel, a master trainer in Boca Raton, Florida.

Why you care: Because engaged glutes mean you'll turbocharge the tush-tightening powers of every lower-body exercise you do.